title: Effects of photodynamic therapy on Gram-positive and Gram-negative bacterial biofilms by bioluminescence imaging and scanning electron microscopic analysis.
abstract: OBJECTIVE
  The aim of this study was to test photodynamic therapy (PDT) as an alternative approach to biofilm disruption on dental hard tissue, We evaluated the effect of methylene blue and a 660 nm diode laser on the viability and architecture of Gram-positive and Gram-negative bacterial biofilms.
  
  
  METHODS
  Ten human teeth were inoculated with bioluminescent Pseudomonas aeruginosa or Enterococcus faecalis to form 3 day biofilms in prepared root canals. Bioluminescence imaging was used to serially quantify and evaluate the bacterial viability, and scanning electron microscopic (SEM) imaging was used to assess architecture and morphology of bacterial biofilm before and after PDT employing methylene blue and 40 mW, 660 nm diode laser light delivered into the root canal via a 300 μm fiber for 240 sec, resulting in a total energy of 9.6 J. The data were statistically analyzed with analysis of variance (ANOVA) followed by Tukey test.
  
  
  RESULTS
  The bacterial reduction showed a dose dependence; as the light energy increased, the bioluminescence decreased in both planktonic suspension and in biofilms. The SEM analysis showed a significant reduction of biofilm on the surface. PDT promoted disruption of the biofilm and the number of adherent bacteria was reduced.
  
  
  CONCLUSIONS
  The photodynamic effect seems to disrupt the biofilm by acting both on bacterial cells and on the extracellular matrix.
authors.affiliation: 1 Department of Orthodontics, São Leopoldo Mandic Dental Research Center , Campinas, São Paulo, Brazil .
authors.forename: Aguinaldo S
authors.initials: AS
authors.lastname: Garcez
authors.forename: Silvia C
authors.initials: SC
authors.lastname: Núñez
authors.forename: Nilton
authors.initials: N
authors.lastname: Azambuja
authors.forename: Eduardo R
authors.initials: ER
authors.lastname: Fregnani
authors.forename: Helena M H
authors.initials: HM
authors.lastname: Rodriguez
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hamblin
authors.forename: Hideo
authors.initials: H
authors.lastname: Suzuki
authors.forename: Martha S
authors.initials: MS
authors.lastname: Ribeiro
mesh_terms: D018441:Biofilms / Q000187:drug effects*; D004396:Coloring Agents / Q000494:pharmacology; D003786:Dental Pulp Cavity / Q000187:drug effects* / Q000382:microbiology*; D013293:Enterococcus faecalis / Q000187:drug effects*; D006801:Humans; D054023:Lasers, Semiconductor; D049449:Luminescence; D008751:Methylene Blue / Q000494:pharmacology; D008855:Microscopy, Electron, Scanning; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000187:drug effects*
chemical_list: D004396:Coloring Agents; D017319:Photosensitizing Agents; D008751:Methylene Blue